We have developed a novel laboratory viscometer which is capable of measuring the shear dependent viscosity of fresh human blood in less than a minute, and which presents the results in the form of model parameters which are functions of hematrocrit, red blood cell properties, and other blood variables. Viscosity has been shown to be an important variable in many human diseases, and changes in viscosity could be used both in diagnosis and in following the course of therapy. However, the present instrument is complicated, requires skill in its use, and depends on a complex method of data analysis. We propose to develop a clinically useful version of this instrument, with modified data analysis built in microprocessing, suitable for application to the clinical situation. The work also will include testing of the instrument and comparison of results with the more sophisticated version in the laboratory, followed by a demonstration test in the clinic. Such an instrument would be of value particularly in cardiovascular and cerebro-vascular disease, and could become a standard diagnostic test for the physical state of blood. The development and laboratory testing will be done in the Department of Bioengineering, and the clinical testing will be carried out in the Geropsyschiatric Research Unit.